System and Method For Treating Tissue Using An Expandable Antenna

ABSTRACT

An ablation device includes an antenna assembly having a radiating portion configured to deliver energy from a power source to tissue of a patient. The radiating portion has an outer conductor and an inner conductor extending therethrough. The inner conductor is disposed within the outer conductor and defines a longitudinal axis. One of the inner conductor and the outer conductor is movable relative to the other to cause at least a portion of the outer conductor to expand radially relative to the longitudinal axis.

BACKGROUND

1. Technical Field

The present disclosure relates to electrosurgical ablation devices andmethods. More particularly, the disclosure relates to treating tissueusing a deployable antenna capable of being expanded.

2. Background of Related Art

In the treatment of diseases such as cancer, certain types of cancercells have been found to denature at elevated temperatures that areslightly lower than temperatures normally injurious to healthy cells.These types of treatments, known generally as hyperthermia therapy,typically utilize electromagnetic radiation to heat diseased cells totemperatures above 41° C. while maintaining adjacent healthy cells atlower temperatures where irreversible cell destruction will not occur.Other procedures utilizing electromagnetic radiation to heat tissue alsoinclude ablation and coagulation of the tissue. Such microwave ablationprocedures, e.g., such as those performed for menorrhagia, are typicallydone to ablate and coagulate the targeted tissue to denature or kill it.Many procedures and types of devices utilizing electromagnetic radiationtherapy are known in the art. Such microwave therapy is typically usedin the treatment of tissue and organs such as the prostate, heart, andliver.

One non-invasive procedure generally involves the treatment of tissue(e.g., a tumor) underlying the skin via the use of microwave energy. Themicrowave energy is able to non-invasively penetrate the skin to reachthe underlying tissue. However, this non-invasive procedure may resultin the unwanted heating of healthy tissue. Thus, the non-invasive use ofmicrowave energy requires a great amount of control. This is partly whya more direct and precise method of applying microwave radiation hasbeen sought.

Presently, there are several types of microwave probes in use, e.g.,monopole, dipole, and helical. One type is a monopole antenna probeconsisting of a single, elongated microwave conductor exposed at the endof the probe. The probe is sometimes surrounded by a dielectric sleeve.The second type of microwave probe commonly used is a dipole antennaconsisting of a coaxial construction having an inner conductor and anouter conductor with a dielectric separating a portion of the innerconductor and a portion of the outer conductor. In the monopole anddipole antenna probe, microwave energy generally radiatesperpendicularly from the axis of the conductor.

Because of the perpendicular pattern of microwave energy radiation,conventional antenna probes are typically designed to be inserteddirectly into the tissue, e.g., a tumor, to be radiated. However, suchtypical antenna probes commonly fail to provide uniform heating axiallyand/or radially about the effective length of the probe.

It is often difficult to assess the extent to which the microwave energywill radiate into the surrounding tissue, i.e., it is difficult todetermine the area or volume of surrounding tissue that will be ablated.Furthermore, when conventional microwave antennas are inserted directlyinto the tissue, e.g., cancerous tissue, there is a potential ofdragging or pulling cancerous cells along the antenna body into otherparts of the body during insertion, placement, or removal of the antennaprobe.

In certain circumstances, it is advantageous to create a relativelylarge ablation region, which often requires multiple ablationinstruments inserted into a patient.

SUMMARY

As used herein the term “distal” refers to that portion of the microwaveablation device, or component thereof, farther from the user while theterm “proximal” refers to that portion of the microwave ablation deviceor component thereof, closer to the user.

According to one aspect of the present disclosure, an ablation device isprovided. The ablation device includes an antenna assembly having aradiating portion configured to deliver energy from a power source totissue of a patient. The radiating portion has an outer conductor and aninner conductor extending therethrough. The inner conductor is disposedwithin the outer conductor and defines a longitudinal axis. One of theinner conductor and the outer conductor is movable relative to the otherto cause at least a portion of the outer conductor to expand radiallyrelative to the longitudinal axis.

Alternatively or in addition, the outer conductor may include aplurality of deployable conductors disposed at least partially along alength thereof configured to expand radially relative to thelongitudinal axis.

Alternatively or in addition, the plurality of deployable conductors maybe configured to mechanically cut through tissue.

Alternatively or in addition, the plurality of deployable conductors maybe configured to cut through tissue with the aid of energy from thepower source.

According to a further aspect of the present disclosure, at least aportion of the outer conductor may be flexible.

Alternatively or in addition, a distance between the outer conductorsand the inner conductor may define an ablation region when the outerconductors are radially expanded relative to the longitudinal axis.

Alternatively or in addition, the outer conductor and the innerconductor may be configured to form an electromagnetic field within theablation region upon actuation thereof.

Alternatively or in addition, distal movement of the outer conductorrelative to the inner conductor may cause at least a portion of theouter conductor to expand radially relative to the longitudinal axis.

Alternatively or in addition, proximal movement of the inner conductorrelative to the outer conductor may cause at least a portion of theouter conductor to expand radially relative to the longitudinal axis.

According to a further aspect of the present disclosure, a method oftreating tissue is provided. The method includes the step of insertingat least a portion of a microwave ablation device into tissue. Themicrowave ablation device includes an inner conductor disposed within anouter conductor. The inner conductor defines a longitudinal axis. Themethod also includes the steps of expanding at least a portion of theouter conductor relative to the longitudinal axis to generate anablation region between the outer conductor and the inner conductor anddelivering energy to at least one of the inner conductor and the outerconductor to treat tissue disposed within the ablation region.

Alternatively or in addition, the expanding step of the method mayfurther comprise the step of moving the inner conductor relative to theouter conductor.

Alternatively or in addition, the expanding step of the method mayfurther comprise the step of moving the outer conductor relative to theinner conductor.

Alternatively or in addition, the method may also include the step ofapplying at least one of a distal force and a proximal force to themicrowave ablation device subsequent to the expanding step to cuttissue.

Alternatively or in addition, the method may also include the step ofproviding energy to the outer conductor subsequent to the expanding stepand prior to the applying step to cut tissue.

Alternatively or in addition, the method may also include the step ofproviding energy to the inner and outer conductors to generate amagnetic field within the ablation region configured to treat tissue.

Alternatively or in addition, the method may also include performing theexpanding step to cut tissue.

According to a further aspect of the present disclosure, anelectrosurgical system for treating tissue is provided. The systemincludes an electrosurgical generator and a microwave ablation device.The microwave ablation device includes a radiating portion configured todeliver energy from the electrosurgical generator to tissue of apatient. The radiating portion has an outer conductor and an innerconductor extending therethrough. The inner conductor is disposed withinthe outer conductor and defines a longitudinal axis. The microwaveablation device also includes a distal tip disposed in mechanicalcooperation with at least one of the outer and inner conductors. One ofthe inner conductor and the outer conductor is movable along thelongitudinal axis relative to the other such that the outer conductorexpands radially relative to the longitudinal axis.

Alternatively or in addition, relative movement of the distal tiptowards the distal end of the outer conductor may cause at least aportion of the outer conductor to expand radially relative to thelongitudinal axis.

Alternatively or in addition, the outer conductor may be configured toseparate into a plurality of conductors along at least a portionthereof. Alternatively or in addition, the conductors may be configuredto expand relative to the longitudinal axis in response to relativeproximal movement of the distal tip.

Alternatively or in addition, the inner conductor may be operablycoupled to the distal tip such that movement of the inner conductoralong the longitudinal axis translates relative movement of the distaltip.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the present disclosure are described herein withreference to the drawings wherein:

FIG. 1 shows a diagram of a microwave antenna assembly in accordancewith an embodiment of the present disclosure;

FIG. 2 is a schematic view of the microwave antenna assembly of FIG. 1connected to a generator;

FIG. 3 is a cross-sectional view taken along section line 3-3 of FIG. 2;

FIG. 4 is a side view of a distal portion of the microwave antennaassembly of FIGS. 1-3;

FIG. 5 is a perspective view of the distal portion of the microwaveablation device of FIGS. 1-4;

FIG. 6A is a side view of the distal portion of the microwave ablationdevice of FIGS. 1-5 unexpanded and disposed within a vessel; and

FIG. 6B is a side view of the distal portion of the microwave ablationdevice of FIGS. 1-6 expanded and disposed within the vessel.

DETAILED DESCRIPTION

Embodiments of the presently disclosed microwave ablation devices aredescribed in detail with reference to the drawings, in which likereference numerals designate identical or corresponding elements in eachof the several views.

An ablation device (e.g., a microwave ablation device) in accordancewith the present disclosure is referred to in the figures as referencenumeral 10. Referring initially to FIG. 1, microwave ablation device 10includes a handle portion 13 and a microwave antenna 12 having a shaftor feedline 14. Feedline 14 includes an outer conductor 20 and an innerconductor 18, that defines a longitudinal axis X-X. A power transmissioncord 21 is shown to connect microwave ablation device 10 to a suitableelectrosurgical generator 22 (see FIG. 2). Additionally, an actuationelement 7 is illustrated in FIG. 1 in accordance with variousembodiments of the present disclosure.

As seen in FIG. 2, a distal tip 30 is disposed adjacent to or coupled toa distal end of inner conductor 18 and/or outer conductor 20. In theillustrated embodiment, the proximal end of feedline 14 includes acoupler 19 that electrically couples antenna 12 to generator 22 viapower transmission cord 21. As will be discussed in further detailbelow, outer conductor 20 includes a distal portion 23 configured toexpand radially relative to longitudinal axis X-X such that distalportion 23 separates into a plurality of radially deployable conductors(e.g., conductors 20 a, 20 b, 20 c, 20 d, and 20 e) upon actuation ofactuation element 7.

Microwave ablation device 10 may be introduced to a treatment site via astraight, arcuate, non-deployable and/or deployable applicator orintroducer. In embodiments, tip 30 is configured to pierce tissue tofacilitate introduction of microwave ablation device 10 to the treatmentsite. Tip 30 may be insulative and/or formed of a dielectric material.

As described above and as shown in FIGS. 2 and 3, feedline 14 may be inthe form of a coaxial cable. Portions of feedline 14 may be flexible andformed of outer conductor 20 surrounding inner conductor 18. Innerconductor 18 and/or outer conductor 20 may be made of a suitableconductive metal that may be semi-rigid or flexible, such as, forexample, copper, gold, or other conductive metals with similarconductivity values. Alternatively, portions of inner conductor 18 andouter conductor 20 may also be made from stainless steel that mayadditionally be plated with other materials, e.g., other conductivematerials, to improve their properties, e.g., to improve conductivity ordecrease energy loss, etc.

With continued reference to FIG. 3, feedline 14 of antenna 12 is shownincluding a dielectric material 28 surrounding at least a portion of alength of inner conductor 18 and outer conductor 20 and/or conductors 20a-20 e surrounding at least a portion of a length of dielectric material28 and/or inner conductor 18. That is, a dielectric material 28 isinterposed between inner conductor 18 and outer conductor 20, to provideinsulation therebetween and may be comprised of any suitable dielectricmaterial.

Referring now to FIGS. 4 and 5, the distal portion 23 of outer conductor20 is separated into a plurality of radially deployable outer conductors20 a, 20 b, 20 c, 20 d, and 20 e. Conductors 20 a-20 e are illustrativeonly in that the distal portion 23 of outer conductor 20 may beseparated into any two or more radially deployable conductors. Outerconductor 20 may be at least partially formed of a flexible materialwherein separation of the distal portion 23 of outer conductor 20 intoconductors 20 a-20 e may be achieved during the manufacturing process bycutting or slicing through the flexible material along at least aportion of the distal portion 23 of outer conductor 20 in multiplelocations around the circumference of distal portion 23. Distal tip 30is in mechanical cooperation with each conductor 20 a-20 e or innerconductor 18. In one embodiment, inner conductor 18 is movable relativeto outer conductor 20 via translation of actuation element 7 (See FIG.1), as discussed in detail below. In another embodiment, outer conductor20 is movable relative to inner conductor 18 and distal tip 30, asdiscussed in detail below. In some embodiments, distal tip 30 is also inelectrical communication with either outer conductors 20 a-20 e or innerconductor 18.

Translation of actuation element 7 (see FIG. 1) causes movement of innerconductor 18 (substantially along longitudinal axis X-X) with respect toouter conductor 20 or vice-versa. More specifically, distal translationof actuation element 7 causes inner conductor 18 to move distally in thedirection of arrow “A” and proximal translation of actuation element 7causes inner conductor 18 to move proximally in the direction of arrow“B.” In response to proximal movement of inner conductor 18, the distalportion 23 of outer conductor 20 is forced or expanded radially relativeto longitudinal axis X-X in the direction of arrow “C” (see FIGS. 4 and5) such that outer conductor 20 separates into conductors 20 a-20 e.Thus, an ablation region 40, as defined by the boundaries of conductors20 a-20 e (including the area between conductors 20 a-20 e and innerconductor 18), is expanded (e.g., widened) as a distance betweenconductors 20 a-20 e and inner conductor 18 becomes larger. In responseto distal movement of inner conductor 18, conductors 20 a-20 e retracttoward longitudinal axis X-X in the direction opposite to arrows “C”.

In embodiments, at least a portion of each conductor 20 a-20 e isflexible to facilitate the radial expansion of conductors 20 a-20 erelative to longitudinal axis X-X. The ablation region 40 may be anelectromagnetic field generated by opposing polarities of innerconductor 18 (e.g., positive) relative to conductors 20 a-20 e (e.g.,negative) for ablating tissue disposed within the ablation region 40.

In one embodiment, translation of actuation element 7 (see FIG. 1)causes movement of outer conductor 20 (substantially along longitudinalaxis X-X) with respect to inner conductor 18 and distal tip 30. In thisembodiment, inner conductor 18 and distal tip 30 are stationary alongthe longitudinal axis X-X. More specifically, distal translation ofactuation element 7 causes outer conductor 20 to move distally in thedirection of arrow “A” and proximal translation of actuation element 7causes outer conductor 20 to move proximally in the direction of arrow“B.” In response to distal movement of outer conductor 20, the distalportion 23 of outer conductor 20 is forced or expanded radially relativeto longitudinal axis X-X, in the direction of arrow “C” (see FIGS. 4 and5) such that outer conductor 20 separates into conductors 20 a-20 e. Inresponse to proximal movement of outer conductor 20, conductors 20 a-20e retract toward longitudinal axis X-X in the direction opposite toarrow “C”.

Each conductor 20 a-20 e may be configured to pierce or slice throughtissue, either mechanically and/or with the aid of energy, e.g.,radiofrequency energy, heat energy, resistive energy, etc. In theembodiment where conductors 20 a-20 e can mechanically pierce or slicethrough tissue, conductors 20 a-20 e may be thin enough to pierce orslice through tissue upon the exertion of a predetermined amount offorce (e.g., the amount of force generated upon retraction of innerconductor 18 and/or radial expansion of conductors 20 a-20 e). In otherwords, antenna 12 is positioned within tissue when conductors 20 a-20 eare disposed in a non-expanded, parallel configuration relative to thelongitudinal axis X-X and then the conductors 20 a-20 e are expanded topierce into and through tissue. As a result thereof, tissue is embeddedwithin the ablation zone 40 for treatment. Additionally oralternatively, conductors 20 a-20 e may be configured to conduct energy,e.g., from generator 22, to slice or pierce through tissue. Deploymentof conductors 20 a-20 e also helps secure the antenna 12 relative to atumor and maintain the antenna 12 in place during treatment.

Referring specifically to FIG. 4, conductors 20 a-20 e are shownradially expanded relative to the longitudinal axis X-X prior toinsertion of antenna 12 into tissue “T”. In this scenario, a distalforce applied to antenna 12 in the direction of arrow “A” causesconductors 20 a-20 e to slice through the tissue “T” such that at leasta portion of tissue “T” is disposed within ablation region 40.

Referring specifically to FIG. 5, antenna 12 is shown inserted into orthrough tissue “T” prior to radial expansion of conductors 20 a-20 erelative to the longitudinal axis X-X. In this scenario, a proximalforce applied to antenna 12 in the direction of arrow “B” causesconductors 20 a-20 e to slice through tissue “T” such that at least aportion of tissue “T” is disposed within ablation region 40.

As discussed above, conductors 20 a-20 e may be configured to pierce orslice through tissue mechanically and/or with the aid of energy fromgenerator 22. In the case of conductors 20 a-20 e utilizing the aid ofenergy from generator 22 to pierce or slice through tissue, conductors20 a-20 e may be energized prior to engagement with tissue “T” or,alternatively, substantially simultaneously therewith.

By retracting and expanding the conductors 20 a-20 e during a procedure,the effective length and impedance of the antenna 12 is changed, therebychanging the performance of the antenna 12. In this manner, the antenna12 may be actively tuned during a procedure.

Referring now to FIGS. 6A and 6B, feedline 14 is shown disposed within avessel “V”. A vessel repairing sealant 50 (e.g., fibrin orelastic/collagen matrix) is disposed between an inner wall of vessel “V”and outer conductor 20 and is configured to repair the inner walls ofvessel “V” once properly deployed. Sealant 50 may be, for example, asleeve and/or a mesh matrix configured to be slid over at least aportion of feedline 14 such that upon deployment of feedline 14 withinvessel “V”, sealant 50 is disposed between the inner surface of vessel“V” and at least a portion of feedline 14. As illustrated in FIG. 6A,feedline 14 is inserted within vessel “V” while conductors 20 a-20 e aredisposed in a non-expanded or retracted state relative to longitudinalaxis X-X. Once feedline 14 is positioned relative to sealant 50 withinvessel “V”, actuation element 7 is translated proximally in thedirection of arrow “F” to retract inner conductor 18, thereby pullingdistal tip 30 proximally to force conductors 20 a-20 e to expandradially relative to longitudinal axis X-X. As discussed above,actuation element 7 may, in certain embodiments, be translated distallyin the direction of arrow “E” to move outer conductor 20 distally toengage distal tip 30, thereby forcing conductors 20 a-20 e to expandradially relative to the longitudinal axis X-X.

In either scenario, radial expansion of conductors 20 a-20 e forcessealant 50 to engage the inner wall of vessel “V” to repair cracks ordamaged areas in the vessel “V”, as shown in FIG. 6B. In embodiments,once sealant 50 engages the inner wall of vessel “V”, generator 22 isconfigured to selectively supply energy (e.g., RF or microwave energy)to conductors 20 a-20 e to activate or cure sealant 50 via thegeneration of heat. That is, sealant 50 may be a mesh matrix havingvessel repairing gel or collagen disposed thereon that is configured toleach to the inner wall of vessel “V” upon the application of heatcaused by the supply of energy through conductors 20 a-20 e and/or innerconductor 18. Examples of such vessel repairing sealants include,without limitation, Evicel® liquid fibrin sealant and the CryoSeal® FSsystem.

Once a desired portion of sealant 50 is applied to the inner wall ofvessel “V”, conductors 20 a-20 e may be radially retracted towardlongitudinal axis X-X via actuation of actuation element 7 such thatantenna 12 is movable proximally (arrow “F”) or distally (arrow “E”)within vessel “V” for purposes of removal therefrom or for purposes ofmovement relative to sealant 50, as shown in FIG. 6A. In this manner,distal portion 23 of outer conductor 20 may be positioned orre-positioned to substantially align with a portion of sealant 50 thathas not yet been forced to engage the inner wall of vessel “V” and/orbeen activated or cured by the application of heat generated by thesupply of energy through conductors 20 a-20 e and/or inner conductor 18.

The described embodiments of the present disclosure are intended to beillustrative rather than restrictive, and are not intended to representevery embodiment of the present disclosure. Various modifications andvariations can be made without departing from the spirit or scope of thedisclosure as set forth in the following claims both literally and inequivalents recognized in law.

What is claimed is:
 1. An ablation device, comprising: an antennaassembly having a radiating portion configured to deliver energy from apower source to tissue of a patient, the radiating portion having anouter conductor and an inner conductor extending therethrough, the innerconductor disposed within the outer conductor and defining alongitudinal axis; wherein one of the inner conductor and the outerconductor is movable relative to the other to cause at least a portionof the outer conductor to expand radially relative to the longitudinalaxis.
 2. An ablation device according to claim 1, wherein the outerconductor includes a plurality of deployable conductors disposed atleast partially along a length thereof configured to expand radiallyrelative to the longitudinal axis.
 3. An ablation device according toclaim 2, wherein the plurality of deployable conductors are configuredto mechanically cut through tissue.
 4. An ablation device according toclaim 2, wherein the plurality of deployable conductors are configuredto cut through tissue with the aid of energy from the power source. 5.An ablation device according to claim 2, wherein at least a portion ofthe outer conductor is flexible.
 6. An ablation device according toclaim 2, wherein a distance between the outer conductors and the innerconductor defines an ablation region when the outer conductors areradially expanded relative to the longitudinal axis.
 7. An ablationdevice according to claim 6, wherein the outer conductor and the innerconductor are configured to form an electromagnetic field within theablation region upon actuation thereof.
 8. An ablation device accordingto claim 1, wherein distal movement of the outer conductor relative tothe inner conductor causes at least a portion of the outer conductor toexpand radially relative to the longitudinal axis.
 9. An ablation deviceaccording to claim 1, wherein proximal movement of the inner conductorrelative to the outer conductor causes at least a portion of the outerconductor to expand radially relative to the longitudinal axis.
 10. Amethod of treating tissue, comprising the steps of: inserting at least aportion of a microwave ablation device into tissue, the microwaveablation device including an inner conductor disposed within an outerconductor and defining a longitudinal axis; expanding at least a portionof the outer conductor relative to the longitudinal axis to generate anablation region between the outer conductor and the inner conductor; anddelivering energy to at least one of the inner conductor and the outerconductor to treat tissue disposed within the ablation region.
 11. Amethod according to claim 10, wherein the expanding step furthercomprises the step of moving the inner conductor relative to the outerconductor.
 12. A method according to claim 10, wherein the expandingstep further comprises the step of moving the outer conductor relativeto the inner conductor.
 13. A method according to claim 10, furthercomprising the step of applying at least one of a distal force and aproximal force to the microwave ablation device subsequent to theexpanding step to cut tissue.
 14. A method according to claim 13,further comprising the step of providing energy to the outer conductorsubsequent to the expanding step and prior to the applying step to cuttissue.
 15. A method according to claim 14, further comprising the stepof providing energy to the inner and outer conductors to generate amagnetic field within the ablation region configured to treat tissue.16. A method according to claim 13, further comprising performing theexpanding step to cut tissue.
 17. An electrosurgical system for treatingtissue, the system including: an electro surgical generator; and amicrowave ablation device, including: a radiating portion configured todeliver energy from the electrosurgical generator to tissue of apatient, the radiating portion having an outer conductor and an innerconductor extending therethrough, the inner conductor disposed withinthe outer conductor and defining a longitudinal axis; a distal tipdisposed in mechanical cooperation with at least one of the outer andinner conductors; wherein one of the inner conductor and the outerconductor is movable along the longitudinal axis relative to the othersuch that the outer conductor expands radially relative to thelongitudinal axis.
 18. An electrosurgical system according to claim 17,wherein relative movement of the distal tip towards the distal end ofthe outer conductor causes at least a portion of the outer conductor toexpand radially relative to the longitudinal axis.
 19. Anelectrosurgical system according to claim 17, wherein the outerconductor is configured to separate into a plurality of conductors alongat least a portion thereof, the conductors being configured to expandrelative to the longitudinal axis in response to relative proximalmovement of the distal tip.
 20. An electrosurgical system according toclaim 17, wherein the inner conductor is operably coupled to the distaltip such that movement of the inner conductor along the longitudinalaxis translates relative movement of the distal tip.